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Optoelectronic Level Switch - Refrigerant

Model OLS-C29

Compact design, refrigerant version with relay output

Selected documents


  • Level measurement for liquid media
  • Level control and monitoring of distinct filling levels
  • Machine building
  • Refrigerator units

Special features

  • Temperature ranges from -30 … +120 °C
  • Exchange of the electronics without opening the vessel, the process connection with the glass prism remains at the vessel
  • Operating states can be read via the LED
  • Various switching delays selectable
  • Relay output


The model OLS-C29 optoelectronic level switches are used for the detection of limit levels in liquids. This is widely independent of physical characteristics such as refractive index, colour, density, dielectric constant and conductivity. Measurement is also done in small volumes.

The switches include an infrared LED and a phototransistor. The light of the LED is directed into a prism. So long as the sensor tip of the prism is in the gas phase,  the light is reflected within the prism to the receptor. When the liquid in the vessel rises and wets approximately 2/3 of the glass tip, the infrared lightbeam into the liquid is interrupted and only a small portion reaches the receptor.

The switching status of the OLS-C29 can be read directly on the sensor.

The electronics can be exchanged without opening the vessel, while the glass prism remains within the vessel

Data Sheet

OLS-C29 Data sheet


OLS Operating Instructions